Internally expanding brake



Feb. 26, 1952 R. B. WATT 2,587,256

INTERNALLY EXPANDING BRAKE Original Filed July 7, 1941 2 SHEETS-SHEET --gl 1 A, -r": F"

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Gttorneg Feb. 26, 1952 vR. B. WATT INTERNALLY EXPANDING BRAKE 2 SHEETS-SHEET 2 Original Filed July 7, 1941 Patented Feb. 26, 1952 lUNITED STATES PATENT" @FFI-CE substituted for application Serial No. 401,347,v

July 7, 1941. '.lhis application-September 27 1946, SeriazlNo'. 699,612

1v claim. (c1. iss-,WI

In brakes of this kind, as at present made, the

brake shoes aren usually formed as levers, each pivoted at one end to the stationary plate. Their opposite ends are moved outwardly by cam or hydraulic action. In this arrangement, owing to the converging relationship between the shoes andthe adjacent part of the brake drum when the brake is off, the pressure exerted by the brake lining on the brake drum is not uniform over the entire length of the brake lining. Further, owing to the position ofthe pivot about which the levers move, such pressure does not act` radially in relation to the interior surface of the brake drum periphery. Thus, with the brakes generally used, it` is impossible to obtain 100% braking of the power ofthe bands.

'I'he object of the present invention'isv to; provide an improved brake construction wherein four brake shoes are simultaneously expanded to cause the brake lining to equally engage the brake drum at all points. Thisfaffords approximately 360 of braking surface ofthe brake lining.

A furtherobject of the invention is to provide a brake drum in which two pairs of shoesare arranged-and mounted upon expander plates in a mannerthat permits the shoes to moveradially and parallel with respect tothe contactface.-

A further object of the invention is to provide means for limiting the outward movement of the brake shoes so as to prevent the lining from Wearing down to the shoe and thus cause scorching of the brake drum.

A further object of the invention is to provide means for balancing the braking movement imparted to the individual shoes.

A still further object of the invention is to provide a brake of simple and sturdy construction and suitable for use with all types of motor vehicles.

With the foregoing and other objects in view I have invented the brake that is the subject matter of this application and which is further described in the following detailed specification and illustrated in the accompanying drawings forming part of this application, and in which:

Figure l'is a plan view oi' the brake mechanism assen'lbled.v Y l Figure 2fis a plan view of the brake mechanism with the shoe expanding members removed and Ythereto in a suitable manner:

with the brakeshoes. in. contracted or neutral position.

Figure 3 is a View similar to Figure2`butwith thebrakeV shoes inpartially expanded; braking position.

Figure 4 is a cross sectional view taken online A 4--4 of FigureZ.

Figure 5'. is ai perspective view of; one of'V the expander members. f

Figure 6L is a. perspective view'of'one ofthe brake shoe segments.r

In the drawings,v in which. like numerals of reference denote similar parts, the numeral 5 generally designates the brake housing or backing plate conventionally incorporated in the road wheel ofa motor vehicle'. Associatedwith the backing plate is a' rotatable drum 6i which. is secured to the wheel, not shown, andprovides anY internal annular friction surface. 1: for engagement with the brake shoes, which'` arev of expanding type..v

In carrying Yout the invention,l I preferably supply a complement ofshjo'es 8 composinga circle within thebrakey drum'. 'I'.l'iefshoes" Bicomprise two opposing sets; one of' which comprises the shoes''and In and the other'of theV shoes Il'and I?. Aswll be evident from the drawings, each shoe' is in the' formV of anv arc of'a circlezjwith theouter face I3 having brake lining" lisecured The` liningconforms 'tothe curvature of vthe drumand'its surface'isW adapted to engage the frictionsurface T of: the drum' G for'brakingthemotionoftlre drum; EachY shoe" is reinforced bv" a suit'abie web I5: which produces* a' brake shoe'` thatI is" T'- shaped in cross section. Each brake shoe is provided with two slots I6, an opening I1 between the slots I i and an unstanding boss I8, the purpose of which will be later described. The web I5 has its inner edge Ill flanged downwardly to strengthen the shoe and add to its rigidity. Also. the web of each brake shoe has a V-shaped portinn 20 cut out at each end thereof.

Integral with and extending upwardly from the backing plate are the rectangular guide lugs and stops 2|. two beiner provided for each brake shoe. These lugs are adapted to t in the slots I6 of the brake shoe. as shown in Figure 2. and are of a size to permit reciprocating movement of the brake shoes. v'I'he brake shoes are radiallyA movable and retained in place by means of the spring tensioned fasteners 22, Figure 4, which` extend through the backing plate and hold the shoes thereto. The brake shoes are guided by means of the slots I6 and lugs 2|. When assembled,v as shown in Figure 2. the cut-out portions 2,0 in

`brake shoes 9, l0, Il and l2. ,cause brake shoes 9 and I0 to move outwardly,

the webs of the brake shoes form square aper tures in the centers of which are the shoe-ad- J'usting members 23 consisting of the cam 24 mounted upon adjustable shafts 25. Turning of the shaft will bring the cam into engagement with the edges of the webs so that the brakes may be properly'adjusted by spreading or contracting the brake shoes.

Tension springs 26 are attached at one end 21 to the brake shoe webs and at the other end to the hub 28 of the backing plate. These tension springs serve to return and retain the shoes in proper spaced relation with respect to the brake drum when the applied force is released.

Mounted on the webs of the brake shoes are two expanders 29. One end of these expanders are pivoted together on pivot pin 30 While the other ends 3l are suitably connected to the opposite ends of a usual operating mechanism of the cylinder 32 of a conventional hydraulic braking system. Each expander 29 is provided with a. long slot 33 and a short slot 34. The long slots receive the upstanding lugs I8 of shoes 9 and Il respectively, while the short slots 34 receive the lugs I8 of shoes I0 and I2 respectively.

Secured to the sides of the expanders next adjacent the Webs l5 are small spacing blocks 35 that keep the expanders suitably spaced from the webs of the brake shoes, and are located so as to be operatively engaged by the cam 24.

In operation, when the brake pedal is applied, the usual hydraulic mechanism will act upon the cylinder 32 and cause the pistons therein to move outwardly. These pistons will, in turn, act upon the ends 3| of the expanders 29 and move them outwardly. The expanders, in moving outwardly, will pivot upon the stationary pivot pin 30. At the same time the pressure of the expanders upon the studs I8 in slots 33 and 34 will cause the studs to be moved outwardly and carry with them the One expander will whilethe other expander will move brake shoes Il and Vl2 in a similar direction. The outward -movement of the brake shoes is limited by the stops 2| thus preventing excessive wear on the brake lining and damage to the brake shoe and y brake drum.

The cams 24 engage the spacing blocks 35 secured to the under sides of the expanders. Thus when adjusting shafts are turned, the eccentrically mounted cams will be rotated to apply A.pressure to the blocks 35, and as rotation is increased, the blocks will be moved outwardly,

carrying with them the expanders 29, and in turn, the brake shoes. This adjustment permits proper positioning of the brake shoes to account for wear on the brake lining.

With the exception of the portions 36, thev brake lining will contact 360 of the drum face and there will be equal gripping or braking pressure at all points.

From the preceding description it will be manifest that this construction provides a simple and practical mechanism of a reliable and serviceable nature. Furthermore, the pressure of the brake shoes is evenly distributed over the entire brake drum surface in a true radial direction and the parts may be assembled or disassembled with ease.

I claim:

In an internal expanding brake mechanism, a non-rotatable backing plate, brake shoes mounted to slide radially upon said backing plate, each brake shoe having spaced slots, guide lugs on the backing plate and positioned within respective slots of the brake shoes, spring means connected between the backing plate and the brake shoes for returning the brake shoes in neutral or inoperative position, a pair of brake shoes, each shoe having a V-shaped notch, the notches being arranged in opposed relationship, spring tensioned fastener means for securing the brake shoes to the backing plate, studs carried by each shoe, expander plates having slots to. receive the studs of the brake shoes for operati/ng al1 of the brake shoes simultaneously, adjusting shafts, a cam fixed to each shaft and disposed between the opposed V-shaped notches of said brake shoes, a spacing block on said expander plates in the path of said cams and means for operating the expander plates.

RAYMOND B. WATT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,620,921 Sanford Mar. 15, 1927 1,707,272 Livingston Apr. 2, 1929 1,832,135 Oliver NOV. 17, 1931 1,853,201 Buscher Apr. 12, 1932 I 1,883,757 Boone Oct. 18, 1932 1,937,691 Girling Dec. 5, 1933 2,100,973 Naylor Nov. 30, 1937 

